Copper sulfate, copper sulfate solution, plating solution, method for producing copper sulfate, method for producing semiconductor circuit board, and method for producing electronic apparatus

ABSTRACT

Copper sulfate which includes a Fe with a concentration of 0.08 ppm by mass or less.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One or more embodiments of the present application relate to coppersulfate, a copper sulfate solution, a plating solution, a method forproducing copper sulfate, method for producing a semiconductor circuitboard, and a method for producing an electronic apparatus.

2. Description of the Related Art

Copper sulfate has been widely used as raw materials for an electrolyticsolution, a pigment, an insecticide, an antiseptic, a mordant, amaterial for battery cells, a medical drug, an electroplating solutionfor electronic components, such as a semiconductor device, and the like.

For example, as copper sulfate capable of being applied to raw materialsfor an electrolytic solution, a pigment, an insecticide, an antiseptic,a mordant, a material for battery cells, a medical drug, anelectroplating solution for electronic components, such as asemiconductor device, and the like, Japanese Patent No. 3,987,069describes high purity copper sulfate having a purity of 99.99% by weightor more and a content of transition metals, such as Fe, Cr, and Ni, of 3ppm by weight or less. Japanese Patent No. 3,943,583 describes highpurity copper sulfate having a purity of 99.999% by weight or more.

However, according to the various demands in recent years, there is anincreasing demand of copper sulfate having a further reduced impuritycontent, as compared to the high purity copper sulfate described inJapanese Patent Nos. 3,987,069 and 3,943,583.

For example, in the case where copper sulfate is used as a raw materialof a copper plating bath, there is a problem that associated to theminiaturization of wiring, iron contained copper sulfate as a rawmaterial for a copper plating bath decreases the conductivity of thecopper film.

One or more embodiments of the present application provide coppersulfate having a reduced iron concentration, a copper sulfate solution,a plating solution, a method for producing copper sulfate, a method forproducing a semiconductor circuit board, and a method for producing anelectronic apparatus.

SUMMARY OF THE INVENTION

Copper sulfate according to one or more embodiments of the presentapplication in one aspect has a Fe concentration of 0.08 ppm by mass orless.

A copper sulfate solution according to one or more embodiments of thepresent application in one aspect has a Fe concentration of 0.019 ppm bymass or less.

A copper sulfate solution according to one or more embodiments of thepresent application in another aspect has a Fe concentration of 0.016ppm by mass or less.

A copper sulfate solution according to one or more embodiments of thepresent application in still another aspect has a Fe concentration of0.012 ppm by mass or less.

A method for producing copper sulfate according to one or moreembodiments of the present application in one aspect contains:concentrating by heating a copper sulfate raw material solution obtainedby dissolving a copper raw material in concentrated sulfuric acid;cooling the copper sulfate raw material solution after concentrating byheating, at a cooling rate of 15° C./hr or less; and recovering adeposit deposited by the cooling in such a manner that a recovery ratioof the deposit becomes from 3 to 50%.

A plating solution according to one or more embodiments of the presentapplication in one aspect has a Fe concentration of 0.018 ppm by mass orless.

A plating solution according to one or more embodiments of the presentapplication in another aspect has a Fe concentration of 0.012 ppm bymass or less.

A method for producing a semiconductor circuit board according to one ormore embodiments of the present application in one aspect containsperforming copper plating by using the aforementioned plating solution.

A method for producing an electronic apparatus according to one or moreembodiments of the present application in one aspect contains producingan electronic apparatus by using a semiconductor circuit board producedby the aforementioned method for producing a semiconductor circuitboard.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The copper sulfate according to one or more embodiments of the presentapplication will be described in detail below.

The copper sulfate according to one or more embodiments of the presentapplication has a Fe concertation of 0.08 ppm by mass or less, and ispreferably copper sulfate having a Fe concentration of 0.05 ppm by massor less. With a Fe concentration in the copper sulfate of 0.08 ppm bymass or less, for example, in the case where the copper sulfateaccording to one or more embodiments of the present application is usedas a raw material of a copper plating solution, the deposition of Fe inthe copper film, and the formation crystal defects generated by thedeposition of Fe can be suppressed. As a result, the electriccharacteristics of a semiconductor wafer, a printed board, and asemiconductor integrated circuit board each having the copper filmformed thereon, or a semiconductor integrated circuit and an electronicapparatus using them can be enhanced. The copper sulfate according toone or more embodiments of the present application may also be used asan electrolytic solution, a pigment, an insecticide, an antiseptic, amordant, a material for battery cells, and the like, and there is apossibility that the copper sulfate can be used as a medical drug or thelike.

The copper sulfate according to one or more embodiments of the presentapplication may be copper sulfate that satisfies any one, any two, anythree, any four, or five of the following items (3-1) to (3-5):

-   -   (3-1) an In concentration of 1.0 ppm by mass or less,    -   (3-2) a Tl concentration of 0.05 ppm by mass or less,    -   (3-3) a Sn concentration of 1.0 ppm by mass or less,    -   (3-4) an Ag concentration of 1.0 ppm by mass or less, and    -   (3-5) an Al concentration of 0.2 ppm by mass or less.

The copper sulfate according to one or more embodiments of the presentapplication may further be copper sulfate that satisfies any one, anytwo, any three, any four, or five of the following items (4-1) to (4-5):

-   -   (4-1) an In concentration of 0.5 ppm by mass or less,    -   (4-2) a Tl concentration of 0.05 ppm by mass or less,    -   (4-3) a Sn concentration of 0.5 ppm by mass or less,    -   (4-4) an Ag concentration of 0.8 ppm by mass or less, and    -   (4-5) an Al concentration of 0.15 ppm by mass.

The copper sulfate according to one or more embodiments of the presentapplication may further be copper sulfate that satisfies any one, anytwo, any three, any four, or five of the following items (5-1) to (5-5):

-   -   (5-1) an In concentration of 0.2 ppm by mass or less,    -   (5-2) a Tl concentration of 0.05 ppm by mass or less,    -   (5-3) a Sn concentration of 0.2 ppm by mass or less,    -   (5-4) an Ag concentration of 0.3 ppm by mass or less, and    -   (5-5) an Al concentration of 0.1 ppm by mass or less.

The copper sulfate according to one or more embodiments of the presentapplication may further be copper sulfate that satisfies any one, anytwo, any three, any four, or five of the following items (6-1) to (6-5):

-   -   (6-1) an In concentration of 0.2 ppm by mass or less,    -   (6-2) a Tl concentration of 0.05 ppm by mass or less,    -   (6-3) a Sn concentration of 0.2 ppm by mass or less,    -   (6-4) an Ag concentration of 0.05 ppm by mass or less, and    -   (6-5) an Al concentration of 0.09 ppm by mass or less.

The copper sulfate according to one or more embodiments of the presentapplication may further be copper sulfate that satisfies any one, anytwo, any three, any four, or five of the following items (7-1) to (7-5):

-   -   (7-1) an In concentration of 0.2 ppm by mass or less,    -   (7-2) a Tl concentration of 0.05 ppm by mass or less,    -   (7-3) a Sn concentration of 0.2 ppm by mass or less,    -   (7-4) an Ag concentration of 0.045 ppm by mass or less, and    -   (7-5) an Al concentration of 0.05 ppm by mass or less.

The concentrations of the elements in the copper sulfate according toone or more embodiments of the present application are measuredaccording to the following manners.

Analysis of Concentrations of Al, Na, K, Co, Cr, Ni, Zn, Ca, Mg, Cd, Mn,and Pb

The concentrations of Al, Na, K, Co, Cr, Ni, Zn, Ca, Mg, Cd, Mn, and Pbin the copper sulfate are analyzed by measuring by an atomic absorptionmethod after removing copper by an electrolytic method. The measurementapparatus used is a flameless atomic absorption device, VarianAA280Z/GTA120, produced by Agilent Technologies, Inc. (Zeeman atomicabsorption spectrophotometer).

1 g of a specimen of copper sulfate and ultrapure water are placed in a10 mL measuring flask, and the specimen is dissolved in ultrapure water.Thereafter, ultrapure water is added to the measuring flask until thebottom of the meniscus of the liquid in the measuring flask reaches themarked line of the measuring flask, so as to produce 10 mL of a coppersulfate aqueous solution. Thereafter, the resulting copper sulfateaqueous solution is subjected to controlled potential electrolysis forfour hours with Pt electrodes (having a Pt concentration of 99.95% bymass or more) for an anode and a cathode (dual electrode system), so asto remove copper from the copper sulfate aqueous solution. Thereafter,the concentrations of Al, Na, K, Co, Cr, Ni, Zn, Ca, Mg, Cd, Mn, and Pbare measured with the aforementioned flameless atomic absorption device.The ultrapure water herein is water having an electroconductivity of0.05882 μS/cm or less (with an electric resistivity (specificresistance) of 17.0 MΩ·cm or more). The precision balance used for themeasurement of the mass of the specimen of copper sulfate is capable ofmeasuring up to four places of decimal. The measured value includes upto four places of decimal. The concentration of the standard specimen ofeach of the elements for the flameless atomic absorption device is 1 ppbby mass. The aforementioned four-hour controlled potential electrolysisis performed in such a manner that electrolysis is performed at acurrent of 0.1 A for 30 minutes, then performed at a current of 0.15 Afor 60 hours, and then performed at a current of 0.25 A for 150 minutes.

The concentrations of the elements are calculated by the followingexpression.

(concertation of designated element (ppm by mass))=(concentration ofdesignated element in copper sulfate aqueous solution (ppb bymass))×(mass of aqueous solution containing collected copper sulfatespecimen dissolved therein (g))/(mass of collected copper sulfatespecimen (g))×10⁻³(ppm by mass/ppb by mass)=(concentration of element incopper sulfate aqueous solution (ppb by mass))×10(g) /1(g)×10⁻³(ppm bymass/ppb by mass)

The mass of specimen of copper sulfate in the calculation expression isa value measured with the precision balance. The mass of the aqueoussolution containing the collected specimen of copper sulfate dissolvedtherein is 10 g.

Analysis of Concentrations of Sn and As

The concentrations of Sn and As in the copper sulfate are analyzed bymeasuring by an atomic absorption method after separating Sn and As fromcopper by the following coprecipitation method. The measurementapparatus used is a flameless atomic absorption device, VarianAA280Z/GTA120, produced by Agilent Technologies, Inc. (Zeeman atomicabsorption spectrophotometer).

2 g of a specimen of copper sulfate, ultrapure water, and 1 mL of a 5%by mass lanthanum nitrate hexahydrate (La(NO₃)₃·6H₂O) aqueous solutionare mixed, and the copper sulfate is dissolved to produce a coppersulfate aqueous solution. Aqueous ammonia is added to the copper sulfateaqueous solution to make pH of the copper sulfate aqueous solution offrom 10 to 11. The hydroxide of copper formed by adding aqueous ammoniais dissolved as a complex of copper and ammonium ion by adding an excessamount of aqueous ammonia. Lanthanum becomes a hydroxide by the additionof aqueous ammonia, and is precipitated along with Sn and As.Thereafter, the precipitate thus formed is separated from the liquidwith filter paper. A 50% by volume nitric acid aqueous solution (volumeof concentrated nitric acid/volume of ultrapure water: 1/1, temperature:50 to 80° C.) is added to the resulting precipitate to dissolve theprecipitate, which is then dried. Thereafter, the product obtained bydrying is dissolved in diluted hydrochloric acid prepared from ultrapurewater and hydrochloric acid (volume of concentrated hydrochloricacid/volume of ultrapure water: 1/9), and the resulting solution isplaced in a 20 mL measuring flask. The concentrated hydrochloric acidused is concentrated hydrochloric acid having a hydrogen chlorideconcentration of 36% by mass. Ultrapure water is added to the measuringflask until the bottom of the meniscus of the liquid in the measuringflask reaches the marked line of the measuring flask, so as to produce20 mL of a solution for measurement. Thereafter, the resulting solutionfor measurement is measured for the concentrations of Sn and As with theaforementioned flameless atomic absorption device. The ultrapure waterherein is water having an electroconductivity of 0.05882 μS/cm or less(with an electric resistivity (specific resistance) of 17.0 MΩ·cm ormore). The precision balance used for the measurement of the mass of thespecimen of copper sulfate is capable of measuring up to four places ofdecimal. The measured value includes up to four places of decimal. Theconcentration of the standard specimen of each of the elements for theflameless atomic absorption device is 50 ppb by mass.

The concentrations of the elements are calculated by the followingexpression.

(concertation of designated element (ppm by mass))=(concentration ofdesignated element in solution for measurement (ppb by mass))×(mass ofsolution for measurement (g))/(mass of copper sulfate specimen(g))×10⁻³(ppm by mass/ppb by mass)=(concentration of designated elementin solution for measurement (ppb by mass))×20 (g)/2(g)×10⁻³(ppm bymass/ppb by mass)

The mass of specimen of copper sulfate in the calculation expression isa value measured with the precision balance. The mass of the solutionfor measurement is 20 g.

Analysis of Concentrations of Fe, In, Tl, Ag, and Ti

The concentrations of Fe, In, Tl, Ag, and Ti in the copper sulfate canbe measured by an ICP-MS method. Specifically, results obtained bymeasuring a specimen of copper sulfate diluted with 500 times ofultrapure water with an ICP mass spectroscope (SPW 9700), produced bySII NanoTechnology Inc.

The analysis of the concentrations of Fe, In, Tl, Ag, and Ti in thecopper sulfate by an ICP-MS method can be performed in the followingmanner.

(1) 1 (g) of a specimen of copper sulfate is collected. The precisionbalance used for the measurement of the mass of copper sulfate iscapable of measuring up to four places of decimal. The measured valueincludes up to four places of decimal.

(2) The specimen of copper sulfate in the item (1) and ultrapure waterare placed in a 500 mL measuring flask, and thereafter ultrapure water(containing diluted nitric acid depending on necessity) is added to themeasuring flask until the bottom of the meniscus of the liquid in themeasuring flask reaches the marked line of the measuring flask, so as toproduce a copper sulfate aqueous solution. The ultrapure water is waterhaving an electroconductivity of 0.05882 μS/cm or less (with an electricresistivity (specific resistance) of 17.0 MΩ·cm or more). Theelectroconductivity of water can be measured according to JIS K0552(1994). The ultrapure water can be produced, for example, by acommercially available ultrapure water producing equipment, such as anultrapure water producing equipment, RFU 400 Series, produced byAdvantec Toyo Kaisha, Ltd.

(3) The concentrations of Fe, In, Tl, Ag, and Ti in the copper sulfateaqueous solution produced in the item (2) are measured with an ICP massspectroscope, such as an ICP mass spectroscope (SPW 9700), produced bySII NanoTechnology Inc. The resulting concentrations of Fe, In, Tl, Ag,and Ti in the copper sulfate aqueous solution are shown by CFe (ppb bymass), CIn (ppb by mass), CTl (ppb by mass), CAg (ppb by mass), and CTi(ppb by mass), respectively.

The concentrations of Fe, In, Tl, Ag, and Ti are calculated by thefollowing expressions.

(Fe concentration (ppm by mass)=(Fe concentration in aqueous solution ofcollected copper sulfate specimen (ppb by mass))×(mass of aqueoussolution of collected copper sulfate specimen (g))/(mass of collectedcopper sulfate specimen (g))×10⁻³(ppm by mass/ppb by mass)=CFe(ppb bymass)×(500(g))×10⁻³(ppm by mass/ppb by mass)/1(g)=0.500×CFe(ppm by mass)

(In concentration (ppm by mass)=(In concentration in aqueous solution ofcollected copper sulfate specimen (ppb by mass))×(mass of aqueoussolution of collected copper sulfate specimen (g))/(mass of collectedcopper sulfate specimen (g))×10⁻³(ppm by mass/ppb by mass)=CIn(ppb bymass)×(500 (g))×10⁻³(ppm by mass/ppb by mass)/1(g)=0.500×CIn(ppm bymass)

(Tl concentration (ppm by mass)=(Tl concentration in aqueous solution ofcollected copper sulfate specimen (ppb by mass))×(mass of aqueoussolution of collected copper sulfate specimen (g))/(mass of collectedcopper sulfate specimen (g))×10⁻³(ppm by mass/ppb by mass)=CTl(ppb bymass)×(500(g))×10⁻³(ppm by mass/ppb by mass)/1(g)=0.500×CTl(ppm by mass)

(Ag concentration (ppm by mass)=(Ag concentration in aqueous solution ofcollected copper sulfate specimen (ppb by mass))×(mass of aqueoussolution of collected copper sulfate specimen (g))/(mass of collectedcopper sulfate specimen (g))×10⁻³(ppm by mass/ppb by mass)=CAg(ppb bymass)×(500 (g))×10⁻³(ppm by mass/ppb by mass)/1(g)=0.500×CAg(ppm bymass)

(Ti concentration (ppm by mass)=(Ti concentration in aqueous solution ofcollected copper sulfate specimen (ppb by mass))×(mass of aqueoussolution of collected copper sulfate specimen (g))/(mass of collectedcopper sulfate specimen (g))×10⁻³(ppm by mass/ppb by mass)=CTi(ppb bymass)×(500 (g))×10⁻³(ppm by mass/ppb by mass)/1 (g)=0.500×CTi(ppm bymass)

The mass of specimen of copper sulfate in the calculation expressions isa value measured with the precision balance. The mass of the solutionfor measurement is 500 g.

Analysis of Concentration of Cl

The Cl concentration (chloride ion concentration) is measured with anion chromatograph. Specifically, the measurement is performed with anion chromatograph (Model ICS-1500), produced by Dionex Corporation.

The analysis of the concentration of Cl in the copper sulfate by an ionchromatograph can be performed in the following manner.

-   -   (1) 1 (g) of a specimen of copper sulfate is collected. The        precision balance used for the measurement of the mass of copper        sulfate is capable of measuring up to four places of decimal.        The measured value includes up to four places of decimal.    -   (2) The specimen of copper sulfate in the item (1) and ultrapure        water are placed in a 100 mL measuring flask, and thereafter        ultrapure water is added to the measuring flask until the bottom        of the meniscus of the liquid in the measuring flask reaches the        marked line of the measuring flask, so as to produce a copper        sulfate aqueous solution. The ultrapure water is water having an        electroconductivity of 0.05882 μS/cm or less (with an electric        resistivity (specific resistance) of 17.0 MΩ·cm or more). The        electroconductivity of water can be measured according to JIS        K0552 (1994). The ultrapure water can be produced, for example,        by a commercially available ultrapure water producing equipment,        such as an ultrapure water producing equipment, RFU 400 Series,        produced by Advantec Toyo Kaisha, Ltd.    -   (³) The concentration of Cl in the copper sulfate aqueous        solution produced in the item (2) is measured with an ion        chromatograph (Model ICS-1500), produced by Dionex Corporation.        The resulting concentration of Cl in the copper sulfate aqueous        solution is shown by CCl (ppb by mass).

The concentration of Cl in the copper sulfate is calculated by thefollowing expression.

(Cl concentration (ppm by mass)=(Cl concentration in aqueous solution ofcollected copper sulfate specimen (ppb by mass))×(mass of aqueoussolution of collected copper sulfate specimen (g))/(mass of collectedcopper sulfate specimen (g))×10⁻³(ppm by mass/ppb by mass)=CCl(ppb bymass)×(100(g))×10⁻³(ppm by mass/ppb by mass)/1(g)=0.100×CCl(ppm by mass)

The mass of specimen of copper sulfate in the calculation expressions isa value measured with the precision balance. The mass of the solutionfor measurement is 100 g.

The copper sulfate according to one or more embodiments of the presentapplication may have a concentration of metal impurities other than Cuof 30 ppm by mass or less in total, 25 ppm by mass or less in total inanother embodiment, 20 ppm by mass or less in total in still anotherembodiment, and 15 ppm by mass or less in total in still further anotherembodiment.

In one or more embodiments of the present application, the“concentrations of metal impurities other than Cu in total” is obtainedin such a manner that Na, K, Co, Cr, Ni, Zn, Al, Ca, Mg, Cd, Mn, Pb, Sn,As, Cl, Fe, Ag, Tl, Ti, and In are analyzed, and the total of theconcentrations of the elements obtained through the analysis isdesignated as the total of concentrations of metal impurities other thanCu.

The concentrations of Fe, In, Tl, Ag, and Sn (ppm by mass) in the coppersulfate are measured in the same manner as described above. The otherelements described above are also measured in the same manner asdescribed above.

The total organic carbon (TOC) concentration in the copper sulfate ispreferably 10 ppm by mass or less, more preferably 5 ppm by mass orless, more preferably 1 ppm by mass or less, and further preferably 0.1ppm by mass or less. The TOC concentration in the copper sulfate may bemeasured with a total organic carbon meter (TOC-V), produced by ShimadzuCorporation. The measurement of the total organic carbon is performedwith a copper sulfate aqueous solution obtained by dissolving a specimenof copper sulfate with ultrapure water (water having an electricresistivity (specific resistance) of 17.0 MΩ·cm or more) to make acopper concentration in the copper sulfate aqueous solution of from 25to 50 g/L. The total organic carbon (TOC) concentration in the coppersulfate is calculated by the following expression.

(total organic carbon concentration (ppm by mass))=(total organic carbonconcentration in aqueous solution of collected copper sulfate specimen(ppb by mass)×(mass of aqueous solution of collected copper sulfatespecimen (g))/(mass of collected copper sulfate specimen (g))×10⁻³(ppmby mass/ppb by mass)

The copper sulfate according to one or more embodiments of the presentapplication may contain anhydrous copper sulfate and/or a hydrate ofcopper sulfate. Examples of the hydrate of copper sulfate include coppersulfate monohydrate, copper sulfate trihydrate, and copper sulfatepentahydrate. The copper sulfate according to one or more embodiments ofthe present application may contain a known hydrate of copper sulfate.In the description herein, the scope of claim, and the abstract, theterm “copper sulfate” used is a concept that includes anhydrous coppersulfate and/or hydrates of copper sulfate.

The copper sulfate according to one or more embodiments of the presentapplication may have a concentration of copper sulfate (which is aconcentration of copper sulfate pentahydrate assuming that the coppersulfate is wholly copper sulfate pentahydrate) of 99.9% by mass or moreand 99.999% by mass or less, 99.9% by mass or more and 99.995% by massor less in another embodiment, 99.9% by mass or more and 99.992% by massor less in still another embodiment, 99.9% by mass or more and 99.99% bymass or less in still further another embodiment, and 99.9% by mass ormore and less than 99.99% by mass in still further another embodiment.

The concentration of copper sulfate is a result of evaluation by thefollowing expression.

The copper concentration in a specimen of copper sulfate is measured bya sodium thiosulfate titration method.

The measurement method of the copper concentration (sodium thiosulfatetitration method) is performed in the following manner.

A designated amount of a specimen of copper sulfate is collected anddissolved in ultrapure water to produce a copper sulfate aqueoussolution having a concentration of copper sulfate of 255 g/L. Theprecision balance used for the measurement of the mass of the specimenof copper sulfate is capable of measuring up to four places of decimal.The ultrapure water herein is water having an electroconductivity of0.05882 μS/cm or less (with an electric resistivity (specificresistance) of 17.0 MΩ·cm or more). The measured value includes up tofour places of decimal. Thereafter, the operations of the followingitems (1) and (2) are performed.

-   -   (1) 2 mL of the copper sulfate aqueous solution is collected, to        which an excess amount of potassium iodide is added.

The following reaction proceeds by adding potassium iodide to the coppersulfate aqueous solution.

2Cu²⁺+4KI→2CuI+I₂+4K⁺

-   -   (2) The measurement is performed by titrating the amount of 12        generated in the reaction in (1) with sodium thiosulfate.        Specifically, the titration is performed until the violet color        of iodine disappears to form a white turbid solution. The amount        (molar amount) of sodium thiosulfate used for the titration is        calculated.

I₂+2Na₂S₂O₃→Na₂S₄O₆+2NaI

It is assumed that the specimen of copper sulfate contains the sameamount (molar amount) of copper as the amount of sodium thiosulfate usedin the titration.

The copper concertation is measured by the following expressions.

(mass of copper contained in copper sulfate specimen (g))=(amount ofcopper contained in copper sulfate specimen (mol))×(atomic weight ofcopper (g/mol))=(amount of sodium thiosulfate required for titratingiodine (I₂)(mol))×(atomic weight of copper (g/mol))

(mass of copper sulfate pentahydrate contained in copper sulfatespecimen (g))=(mass of copper contained in copper sulfate specimen(g)×3.9292009(assuming that the copper sulfate is wholly copper sulfatepentahydrate)

(concentration of copper sulfate (% by mass))=(mass of copper sulfatepentahydrate contained in copper sulfate specimen (g))/(mass of coppersulfate specimen (g))×100 (%)=(mass of copper in copper sulfate specimen(g)×3.9292009/(mass of copper sulfate specimen (g))×100 (%)

The method for producing copper sulfate according to one or moreembodiments of the present application will be described.

A raw material containing copper and a concentrated sulfuric acidaqueous solution are heated in a reaction vessel under stirring todissolve the raw material containing copper in the concentrated sulfuricacid aqueous solution, thereby providing a copper sulfate raw materialsolution. The stirring means is not particularly limited, and forexample, the solution can be stirred by blowing air therein.

The raw material containing copper used may be commercially availablecopper sulfate crystals (concentration: 95 to 99.9% by mass). The coppersulfate crystals contain impurities, such as Na, Mg, Al, Ca, In, Sn, Ag,and Fe. In alternative, a solution obtained by dissolving electrolyticcopper having a purity of 99.99% or more in an aqueous solution ofconcentrated sulfuric acid may also be used as the raw materialcontaining copper. The concentrated sulfuric acid used may becommercially available concentrated sulfuric acid (sulfuric acidconcentration: 95 to 99.9% by mass). Water used in the aqueous solutionof concentrated sulfuric acid is preferably ultrapure water. Theultrapure water preferably has an electric resistivity of 15 MΩ·cm ormore. This is because the use of ultrapure water having an electricresistivity of 15 MΩ·cm or more may reduce the impurities, such as Na,Mg, Al, Ca, In, Sn, Ag, and Fe in the aqueous solution of concentratedsulfuric acid in some cases, and may decrease the concentrations ofelements, such as Fe, in the resulting copper sulfate in some cases. Theelectric resistivity of the ultrapure water is more preferably 15.5MΩ·cm or more, more preferably 16.0 MΩ·cm or more, more preferably 16.5MΩ·cm or more, and more preferably 17.0 MΩ·cm or more.

Subsequently, by heating the copper sulfate raw material solution, forexample, to from 40 to 100° C., preferably approximately 100° C., waterin the copper sulfate raw material solution is evaporated, and thecopper sulfate raw material solution is concentrated until the copperconcentration thereof becomes, for example, from 100 to 250 g/L. Theconcentrated copper sulfate raw material solution is then graduallycooled in the reaction vessel, and thereby crystals of copper sulfate(for example, copper sulfate pentahydrate) can be deposited.

In the cooling step, it is necessary to control precisely the coolingtemperature until the temperature of the copper sulfate raw materialsolution after concentrating by heating becomes the cooling completiontemperature, so as to make the appropriate cooling rate. Specifically, alower cooling rate may provide a condition closer to the equilibrium,providing a tendency that the impurities are hardly contained in thedeposited copper sulfate, but the impurities remain in the coppersulfate raw material solution. Accordingly, with a lower cooling rate,the concentrations of elements other than the elements (Cu, S, O, and H)constituting copper sulfate pentahydrate, such as aluminum, in thedeposited copper sulfate can be decreased.

Specifically, the cooling rate of the copper sulfate raw materialsolution (i.e., the rate of decreasing the temperature of the coppersulfate raw material solution) until the temperature of the coppersulfate raw material solution under concentrating by heating (forexample, 100° C.) becomes the cooling completion temperature is 15°C./hr or less, more preferably 10° C./hr or less, further preferably 7°C./hr or less, and still further preferably 5° C./hr or less. Thecooling means is not particularly limited, and for example, such coolingmethods as water cooling, gradual cooling, air cooling, and cooling witha heat exchanger may be utilized.

A deposit of copper sulfate is obtained from the copper sulfate rawmaterial solution through the cooling step. The resulting copper sulfatecontains copper sulfate pentahydrate as a major component in many cases.The resulting deposit of copper sulfate is separated by solid-liquidseparation, dried, then pneumatically conveyed, and packagedindividually, and thus the copper sulfate (crystal product) according toone or more embodiments of the present application is obtained.

In the cooling step, the recovery condition of the deposit of coppersulfate is preferably regulated. Specifically, the deposit that isdeposited in the initial state in the cooling step is selectivelyrecovered, and thereby the deposit of copper sulfate having a smalleramount of impurities can be recovered. More specifically, the deposit ofcopper sulfate is preferably recovered in such a manner that therecovery ratio of the deposit deposited by cooling becomes from 3 to50%, more preferably from 5 to 35%, and further preferably from 5 to25%. The recovery ratio can be evaluated by the following expression.

(recovery ratio (%))=(copper concentration in original copper sulfateaqueous solution (g/L))−(copper concentration in copper sulfate aqueoussolution at stoppage of deposition of copper sulfate (g/L))/(copperconcentration in original copper sulfate aqueous solution (g/L×100))

The method for making the recovery ratio of the deposit of coppersulfate in a range of from 3 to 50% is preferably, for example, a methodof completing the recovery of the deposit of copper sulfate at the timewhen the temperature of the copper sulfate aqueous solution at therecovery of copper sulfate (i.e., the cooling completion temperature)becomes from 50 to 90° C., more preferably from 50 to 80° C.

The copper sulfate solution according to one or more embodiments of thepresent application can be obtained by adding a solvent, such asultrapure water, to the copper sulfate (crystal product) according toone or more embodiments of the present application, and dissolving thecopper sulfate in the solvent. Examples of the solvent for dissolvingthe copper sulfate include water, one or plural organic solvents, one orplural inorganic solvents, and a solvent containing one or more selectedfrom the group consisting of water, one or plural organic solvents, andone or plural inorganic solvents. The organic solvent used may be analcohol, an aromatic hydrocarbon, a fatty acid, a linear hydrocarbon, acyclic hydrocarbon, an organic acid, or the like. The inorganic solventused may be an inorganic acid, such as sulfuric acid, hydrochloric acid,nitric acid, and hydrofluoric acid. In the case where water is used asthe solvent, a copper sulfate aqueous solution can be obtained.

Ultrapure water that is used for the copper sulfate aqueous solutionpreferably has an electric resistivity of 15.0 MΩ·cm or more, morepreferably 15.5 MΩ·cm or more, more preferably 16.0 MΩ·cm or more, morepreferably 16.5 MΩ·cm or more, and more preferably 17.0 MΩ·cm or more.This is because the use of ultrapure water having an electricresistivity of 15 MΩ·cm or more may decrease the concentrations ofimpurities, such as Na, Mg, Al, Ca, In, Sn, Ag, and Fe in the coppersulfate aqueous solution in some cases.

The copper sulfate solution may have a copper concentration ofapproximately from 50 to 100 g/L. The copper sulfate solution preferablyhas a Fe concentration of 0.019 ppm by mass or less, more preferably0.016 ppm by mass or less, and further preferably 0.012 ppm by mass orless. The copper sulfate solution preferably has a TOC concentration of1.20 ppm by mass or less. The copper sulfate solution more preferablyhas a TOC concentration of 1.10 ppm by mass or less, further preferably1.0 ppm by mass or less, and still further preferably 0.9 ppm by mass orless.

A plating solution can be produced by using the copper sulfate or thecopper sulfate solution described above. The plating solution accordingto one or more embodiments of the present application has a Feconcentration of 0.018 ppm by mass or less, and preferably 0.012 ppm bymass or less.

The plating solution according to one or more embodiments of the presentapplication may satisfy any one, any two, any three, any four, or fiveof the following items (8-1) to (8-5):

-   -   (8-1) an In concentration of 0.2 ppm by mass or less,    -   (8-2) a Tl concentration of 0.01 ppm by mass or less,    -   (8-3) a Sn concentration of 0.3 ppm by mass or less,    -   (8-4) an Ag concentration of 0.4 ppm by mass or less, and    -   (8-5) an Al concentration of 0.04 ppm by mass or less.

The plating solution according to one or more embodiments of the presentapplication may further satisfy any one, any two, any three, any four,or five of the following items (9-1) to (9-5):

-   -   (9-1) an In concentration of 0.13 ppm by mass or less,    -   (9-2) a Tl concentration of 0.01 ppm by mass or less,    -   (9-3) a Sn concentration of 0.2 ppm by mass or less,    -   (9-4) an Ag concentration of 0.3 ppm by mass or less, and    -   (9-5) an Al concentration of 0.020 ppm by mass or less.

The plating solution according to one or more embodiments of the presentapplication may further satisfy any one, any two, any three, any four,or five of the following items (10-1) to (10-5):

(10-1) an In concentration of 0.08 ppm by mass or less,

-   -   (10-2) a Tl concentration of 0.01 ppm by mass or less,    -   (10-3) a Sn concentration of 0.1 ppm by mass or less,    -   (10-4) an Ag concentration of 0.2 ppm by mass or less, and    -   (10-5) an Al concentration of 0.013 ppm by mass or less.

The plating solution according to one or more embodiments of the presentapplication preferably has a copper concentration of from 50 to 100 g/L,and more preferably from 50 to 90 g/L.

The plating solution according to one or more embodiments of the presentapplication can be prepared by using the aforementioned copper sulfatehaving a purity of 99.9% by mass or more and 99.999% by mass or less,and copper plating can be performed by using the plating solution.According to one or more embodiments of the present application, anelectronic apparatus can be produced by using a semiconductor circuitboard produced by performing copper plating by using the platingsolution.

EXAMPLES

While examples of one or more embodiments of the present application aredescribed below along with comparative examples, the examples areprovided for better understanding of one or more embodiments of thepresent application and the advantages thereof, but do not intend torestrict one or more embodiments of the present application.

As a copper raw material, commercially available copper sulfate (Cu: 99%or more, Na: 10 ppm, Mg: 1.5 ppm, Al: 4.5 ppm, Ca: 3.9 ppm, In: 5.6 ppm,Sn: 10 ppm, Ag: 3.5 ppm, Fe: 8.5 ppm) was mixed with ultrapure waterhaving an electric resistivity of 15 MΩ·cm or more, and stirred underheating at 100° C. to produce a copper sulfate raw material solution.Thereafter, the copper sulfate raw material solution was transferred toa concentrating vessel and retained at a temperature of 100° C. for from2 to 10 hours to evaporate water in the copper sulfate raw materialsolution, thereby concentrating the solution until the copperconcentration thereof becomes from 150 to 250 g/L. The copper sulfateraw material solution having been concentrated by heating wastransferred to a crystallizing vessel, and in the crystallizing vessel,cooled to a temperature shown in Table 1 at a cooling rate shown inTable 1. The treated product obtained by cooling was subjected tosolid-liquid separation by suction filtration, and thus a deposit ofcopper sulfate (copper sulfate pentahydrate) was obtained. The depositof copper sulfate was dried to provide a crystal product of the coppersulfate of Examples 1 to 6 and Comparative Examples 1 to 3.

The copper sulfate according to Examples 1 to 6 and Comparative Examples1 to 3 was measured for the concentrations of Na, K, Co, Cr, Ni, Zn, Al,Ca, Mg, Cd, Mn, Pb, Sn, As, Cl, Fe, Ag, Tl, Ti, and In, in coppersulfate and the concentration of copper sulfate by the aforementionedmeasurement methods. The impurity elements in copper sulfate wereassumed to be Na, K, Co, Cr, Ni, Zn, Al, Ca, Mg, Cd, Mn, Pb, Sn, As, Cl,Fe, Ag, Tl, Ti, and In, and the total of the analysis results of theconcentrations of these elements was designated as the totalconcentration of impurities other than Cu. The measurement results ofthe concentrations of Fe, Al, In, Tl, Sn, and Ag in copper sulfate, thetotal concentration of impurities, and the concentration of totalorganic carbon (TOC) in the copper sulfate according to Examples 1 to 6and Comparative Examples 1 to 3 are shown in Table 1.

Copper sulfate aqueous solutions were produced with the copper sulfateaccording to Examples 1 to 6 and Comparative Examples 1 to 3, to whichthe prescribed additives shown later were added to produceelectroplating solutions. An SiO₂ film was accumulated on a siliconwafer by a chemical vapor deposition (CVD) method. A Ta layer as abarrier layer was provided on the surface of the SiO₂ film bysputtering. A Cu seed layer having a thickness of 80 nm was furtherformed on the Ta layer by sputtering, and then a copper film having athickness of 30 μm was formed by copper electroplating. A specimen of 45g was collected from each of the copper sulfate according to Examples 1to 6 and Comparative Examples 1 to 3, and the specimen was dissolvedwith ultrapure water (having an electric resistivity of 17 MΩ·cm ormore) to prepare 200 mL of a copper sulfate aqueous solution (which hadthe same ratio of copper sulfate and the other liquids as theelectroplating bath shown below). The copper sulfate aqueous solutionwas measured for the Fe concentration and the total organic carbonconcentration therein by the aforementioned measurement methods, inwhich the specimen of copper sulfate was replaced with the coppersulfate aqueous solution. The results are shown in Table 2.

The electroplating bath and the electroplating conditions are asfollows.

(Electroplating Bath and Electroplating Conditions) Electroplating Bath

A plating bath having the following composition was used as theelectroplating bath.

Copper sulfate (added as copper sulfate pentahydrate, copper: 57.3 g/L)concentration: 225 g/L

Sulfuric acid concentration: 55 g/L

Chloride ion: 60 ppm

Polyethylene glycol (average molecular weight: 10,000) concentration:500mg/L

Bis(3-sulfopropyl) disulfide (SPS) concentration: 20 mg/L

Janus green concentration: 1 mg/L

The solvent used as ultrapure water (having an electric resistivity of15 MΩ·cm or more).

Electroplating Conditions

The plating conditions were a plating bath temperature of 40° C., acathode current density of 2.0 A/dm², an anode current density of 2.0A/dm², and a plating time of from 70 to 90 minutes.

The copper film was evaluated for platability by measuring the electricresistance by the four-probe method. In the evaluation of platability,the case where the electric resistance was less than 0.020×10⁻⁴ Ω/cm wasevaluated as “A”, the case where the electric resistance was 0.020×10⁻⁴Ω/cm or more and less than 0.040×10⁻⁴ Ω/cm was evaluated as “B”, and thecase where the electric resistance was 0.040×10⁻⁴ Ω/cm or more wasevaluated as “C”. The results are shown in Table 2.

The recovery ratio of the copper sulfate was evaluated according to thefollowing.

(recovery ratio (%))=(copper concentration in original copper sulfateaqueous solution (g/L))−(copper concentration in copper sulfate aqueoussolution at stoppage of deposition of copper sulfate (g/L))/(copperconcentration in original copper sulfate aqueous solution (g/L))

The results are shown in Table 1.

TABLE 1 Cooling rate of copper sulfate raw material solution from 100°C. to Cooling cooling completion completion Recovery Copper sulfateInpurity concentration in copper sulfate (ppm by mass) TOC temperaturetemperature ratio concentration Total (ppm by (° C./hr) (° C.) (%) (% bymass) Fe Al In Ti Sn Ag concentration mass) Example 1  5° C./hr 76 599.999 0.02 0.02 <0.05 <0.05 <0.05 0.15 1.52 0.18 Example 2  7° C./hr 738 99.999 0.03 0.05 0.35 <0.05 0.30 0.60 2.36 0.89 Example 3 10° C./hr 6716 99.995 0.044 0.07 0.42 <0.05 0.61 0.83 17.02 3.33 Example 4 10° C./hr65 18 99.99 0.05 0.09 0.52 <0.05 0.71 1.10 21.35 3.81 Example 5 10°C./hr 60 25 99.99 0.06 0.11 0.59 <0.05 0.79 1.15 25.98 4.32 Example 615° C./hr 53 32 99.99 0.08 0.15 0.66 <0.05 0.91 1.55 28.13 5.26Comparative 15° C./hr 0 75 99.97 3.00 2.30 1.50 <0.05 2.60 2.50 35.5611.45 Example 1 Comparative 15° C./hr 25 64 99.999 0.09 0.09 0.10 <0.050.50 <0.01 1.70 5.72 Example 2 Comparative 15° C./hr 25 55 99.99 0.500.10 0.11 <0.05 0.60 0.04 3.41 6.90 Example 3

TABLE 2 Inpurity concentration in copper TOC Electric sulfate solution(ppm by mass) (ppm by resistance Fe Al In Ti Sn Ag mass) Platability (⁻⁴Ω cm) Example 1 0.005 0.005 <0.01 <0.01 <0.01 0.034 0.04 A 0.0221Example 2 0.007 0.011 0.079 <0.01 0.068 0.135 0.20 B 0.0235 Example 30.010 0.016 0.095 <0.01 0.137 0.187 0.75 B 0.0321 Example 4 0.011 0.0200.117 <0.01 0.160 0.248 0.86 B 0.0333 Example 5 0.014 0.025 0.133 <0.010.178 0.259 0.97 B 0.0349 Example 6 0.018 0.034 0.149 <0.01 0.205 0.3491.18 B 0.0362 Comparative 0.675 0.518 0.338 <0.01 0.585 0.563 2.58 C0.0704 Example 1 Comparative 0.020 0.020 0.023 <0.01 0.113 <0.002 1.29 C0.0401 Example 2 Comparative 0.113 0.023 0.025 <0.01 0.135 0.009 1.55 C0.0422 Example 3

In Examples 1 to 6, in which the cooling rate and the recovery ratio ondepositing copper sulfate pentahydrate from the copper sulfate rawmaterial solution were controlled to adequate ranges, the Feconcentration was decreased to 0.08% by mass or less, and goodplatability was obtained. Furthermore, the Fe concentration of thecopper sulfate solution was 0.08% by mass or less, and further 0.02% bymass or less, and thus good platability was obtained. In ComparativeExample 1 with cooling to 0° C. at a too large cooling rate, on theother hand, the recovery ratio was as high as approximately 70%, but Fewas not reduced, and good platability was not obtained. In ComparativeExamples 2 and 3, copper films were formed under the same conditions asin Example 1 by using copper sulfate produced according to the methodsfor producing high purity copper sulfate described in Japanese PatentNo. 3,987,069 for Comparative Example 2 and Japanese Patent No.3,943,583 for Comparative Example 3. In both Comparative Examples 2 and3, the iron concentration was larger than in Examples 1 to 6 althoughthe copper sulfate concentration was large, and thus the copper film hada large electric resistance, providing inferior platability to Examples1 to 6.

By using a plating solution having the aforementioned composition,wiring formation on a semiconductor wafer, particularly a semiconductorwafer having a through silicon via, can be performed. Furthermore, byusing a plating solution having a composition other than as describedabove, for example a known composition, such as the compositiondescribed in Japanese Patent No. 5,388,191, wiring formation on asemiconductor wafer and wiring formation on a semiconductor circuitboard can be performed. Accordingly, by using a plating solution havingthe aforementioned composition, an integrated circuit and asemiconductor circuit board, such as a package board having theintegrated circuit mounted, can be formed.

What is claimed is:
 1. A plating solution comprising a Fe with aconcentration of 0.018 ppm by mass or less.
 2. The plating solutionaccording to claim 1, wherein the plating solution further comprises anyone, any two, any three, any four, or five of the following items (8-1)to (8-5): (8-1) an In with a concentration of 0.2 ppm by mass or less,(8-2) a Tl with a concentration of 0.01 ppm by mass or less, (8-3) a Snwith a concentration of 0.3 ppm by mass or less, (8-4) an Ag with aconcentration of 0.4 ppm by mass or less, and (8-5) an Al withconcentration of 0.04 ppm by mass or less.
 3. The plating solutionaccording to claim 1, wherein the plating solution further comprises anyone, any two, any three, any four, or five of the following items (10-1)to (10-5): (10-1) an In with a concentration of 0.08 ppm by mass orless, (10-2) a Tl with a concentration of 0.01 ppm by mass or less,(10-3) a Sn with a concentration of 0.1 ppm by mass or less, (10-4) anAg with a concentration of 0.2 ppm by mass or less, and (10-5) an Alwith a concentration of 0.013 ppm by mass or less.
 4. The platingsolution according to claim 1, wherein the plating solution has a copperconcentration of from 50 to 100 g/L.
 5. The plating solution accordingto claim 1, wherein the plating solution has a copper concentration offrom 50 to 90 g/L.
 6. A method for producing a semiconductor circuitboard comprising performing copper plating by using the plating solutionaccording to claim
 1. 7. A method for producing an electronic apparatuscomprising producing an electronic apparatus by using a semiconductorcircuit board produced by the method for producing a semiconductorcircuit board according to claim 6.